There is a case in which a fiber reinforced composite material (for example, carbon fiber reinforced plastic; CFRP) made of combination of a fiber component and a resin component is used for a skin (an outer plate) in a main wing member etc. of an aircraft. There is a case in which a stringer (longitudinal penetrating member) is attached to the skin to increase strength. The skin to which the stringer is attached is hereinafter referred to as a reinforced structure. There is a case in which the fiber reinforced composite material is used for the stringer as well as the skin.
In manufacturing the reinforced structure, a cured stringer is disposed on an uncured skin via adhesive. Then, the skin is cured with heat, pressure etc. and the stringer is bonded integrally to the skin.
Note that there is a case in which the cured stringer is processed before being placed on the skin for size adjustment etc. If the processing has been performed, the fiber components are exposed from a processed surface. In other words, a fiber exposed surface is formed in a part of the stringer. There is a case in which current or voltage is applied to the reinforced structure during operation. For example, if the reinforced structure is used as the main wing member of the aircraft, there is a case in which lightning current or high voltage is applied by lightning etc. Thus, there is a case in which edge glow occurs in the fiber exposed surface.
Techniques for preventing the edge glow are disclosed in Patent Literature 1 (US Patent Publication No. 2008/0,128,430). Patent Literature 1 discloses an idea of applying an edge seal made of a thermosetting resin to the fiber exposed surface, an idea of curing the applied edge seal, an idea in which the edge seal includes carbon fibers and so on.